Abstract
Organotins present a toxicological risk to biota in the aquatic environment. Understanding the behaviour of these compounds in sediment is challenging, with sophisticated analytical techniques required for their measurement. We investigated the use of silica-bound sorbents for diffusive gradients in thin-films (DGT) adsorption gels to pre-concentrate five organotins (monobutlytin (MBT), dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPhT), triphenyltin (TPhT)) found frequently in coastal sediment. C8 sorbent showed optimum performance in uptake and recovery of organotins for pH and ionic strength ranges typical of coastal waters. Recoveries from adsorption gels deployed in filtered sea water were MBT = 123 ± 20%, DBT = 75 ± 12%, TBT = 81 ± 16%, DPhT = 72 ± 30%, TPhT = 58 ± 10% respectively. Devices were used to investigate DGT fluxes and pore water concentrations of organotins in coastal sediment collected from a contaminated site. DGT fluxes measured in sediment cores for the five organotins ranged between 4.3 × 10−8 and 1.6 ×10−5ngcm2s−1. The depletion of organotin species within pore waters at the interface with DGT devices was measured over a series of deployment times (2, 7, 14, 21 and 28 days) and provided estimates of the concentration of organotins in pore waters at Langstone Harbour, UK, prior to depletion by the DGT device and information on their spatial heterogeneity. The novel in situ DGT device developed can pre-concentrate organotins from pore waters in coastal sediment core samples and allows their detection at low environmental concentrations using conventional gas chromatographic/mass spectrometric instrumentation. Use of the DGT device overcomes many problems associated with the conventional pore water sampling of organotins. Our preliminary data suggests it has potential in the future to be a useful tool in investigating the environmental fate of these pollutants. The use of the C8 gel will also allow for the simultaneous sequestration of other semi- and non-polar analytes present in the pore water.
Highlights
Organotins are the most widely used organometallic compounds globally (~ 50,000 t yr−1) [1] with applications in the stabilisation of plastics, precursors in glass coating and as antifungal agents in textiles and other household items [2]
From the 1950s-2001, the major use of tributyltin (TBT) and triphenyltin (TPhT) was as a toxicant in antifoulant paints [2]. Due to their high toxicity to non-target organisms [3,4,5,6] and persistence in the aquatic environment (half-life of TBT > 10 years in anoxic marine sediment, degrading to dibutyltin (DBT) and monobutlytin (MBT)), use of these compounds as antifoulants is banned under the International Convention on the Control of Harmful Anti-fouling Systems on Ships [7]
Many coastal and marine sediments remain contaminated with TBT and other organotins, and the management of such sediments remains an issue for policy makers and regulators
Summary
Organotins are the most widely used organometallic compounds globally (~ 50,000 t yr−1) [1] with applications in the stabilisation of plastics, precursors in glass coating and as antifungal agents in textiles and other household items [2]. From the 1950s-2001, the major use of tributyltin (TBT) and triphenyltin (TPhT) was as a toxicant in antifoulant paints [2] Due to their high toxicity to non-target organisms [3,4,5,6] and persistence in the aquatic environment (half-life of TBT > 10 years in anoxic marine sediment, degrading to dibutyltin (DBT) and monobutlytin (MBT)), use of these compounds as antifoulants is banned under the International Convention on the Control of Harmful Anti-fouling Systems on Ships [7]. We describe the development of a novel DGT method, comprising of an octylsilyl (C8) adsorption layer, suitable for measuring fluxes and interfacial concentrations of MBT, DBT, TBT, DPhT and TPhT in coastal sediment pore waters. This new approach to interpreting DGT data has potential to further our understanding of the behaviour of organotins in situ and could be used as a tool to aid in monitoring, risk or impact assessments at coastal and open sea sites used for the disposal of contaminated dredge material from ports or harbours
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